The present invention relates to a fastener system for attaching a turbojet engine casing to a mounting bar.
The general solution for fastening a turbojet engine to a mounting bar comprises forming flanges on the turbojet engine casing and passing a hollow pin through apertures in the flanges and a corresponding aperture in the mounting bar attached to the aircraft. The hollow pin may pass through sleeves retained in the apertures and be locked in position by a bolt passing through the hollow pin.
In typical known fastener systems, assembly and disassembly of the bolt passing through the hollow pin and holding the assembly together requires access to both ends of the bolt, located on opposite sides of the engine casing flanges. Typically, such access is extremely difficult due to the complex structure of the engine and requires a lengthy disassembly time to remove the engine from the mounting bar.
Attempts have been made to alleviate this problem. A typical example is illustrated in French Pat. No. 2,565,320 which discloses an engine mounting system wherein the bolt has a head portion that is eccentric with respect to the axis of its shank. The maximum radial dimension of the head is less than the inside diameter of the opening in the sleeves extending through the engine casing flanges, but greater than the diameter of the opening extending through the hollow pin. In this system, the bolt is passed through the aligned apertures of the mounting flanges and the mounting bar, and the hollow pin is passed over the shank of the bolt so as to also extend through these openings. The nut on the exposed end of the bolt is then applied and tightened to hold the system in place.
A drawback of this system is that the bolt must be placed into the sleeves and the openings prior to the insertion therethrough of the hollow pin, thus entailing the possibility of damaging the sleeves lining the openings. Also, if the bolt were to break during the operation of the engine, the broken bolt end may pull out of the assembly, no longer holding the hollow pin in place. Should the hollow pin slip out of the openings in either of the flanges or the mounting bar, the engine casing would be released from its suspension structure, possibly resulting in a catastrophic failure of the airframe.